1. Field of the Invention
The present invention relates to an apparatus, namely a sewing machine, adapted to sew an over-edge butt-seam stitch in thick workpieces, for example, tufted carpet.
2. Description of Related Art
For economical reasons, many carpet manufacturers have installed in their mills equipment which performs certain manufacturing or finishing operations, such as dyeing, on a substantially continuous basis. Other such operations include latex application and pile shearing. The tufting of carpet, however, generally involves tufting yarn through a backing of a given width (12 feet, for example) and of a finite length, with the product coming from the tufting operation being wound onto rolls. Thus, in order to take full advantage of continuous dyeing equipment or other continuous processing equipment, the trail edge of one roll of tufted carpet must be secured to the leading edge of the following roll of carpet, and the securing process must be repeated for each successive roll used in the continuous process.
The securing of the edges of tufted carpet has presented numerous problems which have heretofore remained unsolved. Sewing or stitching the edges to one another has been regarded as the most economically viable approach to securing the edges. Specifically, it is believed that an over-edge stitch, to create what is termed a butt-seam, is the preferred means for joining the edges. A particular complication involved in producing an over-edge sewn seam joining edges of workpieces is that existing sewing machines are not capable of satisfactorily sewing materials having the thickness of a carpet pile, which may commonly be in the range of about 1/4 inch to 3/4 inch, and possibly even greater thicknesses. Existing machines instead are generally designed to produce seams in materials such as woven polypropylene, used in making flexible bulk container bags, which material is of a much lower thickness.
Examples of existing machines for sewing over-edge stitches are those sold by Union Special as Model No. 81500A and Model No. 81500B. The Model 81500A is described as being a one needle, two-thread over-edge machine for seaming heavy jute bags and sacks, and the Model 81500B is described as being essentially the same machine, with the added feature of a lifting upper feed for sewing heavy woven polypropylene stacking materials (container bags). The use of an over-edge stitch in seaming the carpet edges presents an additional problem in that the edges of the two rolls of carpet joined by the seam must lie substantially flat once stitched together, in order to prevent complications in the dyeing and other equipment. In sewing an over-edge seam with these existing machines, the edges of the materials to be sewn together are presented laying on top of one another. The stitches and seam produced by the Union Special machine are relatively tight, and do not permit the two workpieces and seam to be flattened out into an edge-abutting configuration, as it is not generally required that the seam be flattened in bag and sack fabrication.
Any attempt to flatten the edges at the seam made with existing machines would create additional stresses or stress concentration areas in the thread and at the carpet edges. Because a large amount of stress is experienced by the seams during the processing of the carpet, it is not advisable to attempt to "make do" with seams produced by the existing machine. Seam breaks or other failures at the seam area require shutting down the dyeing or other operation for a long period of time while the carpet is extracted from the equipment, thereby causing substantial losses in equipment down time.
One machine currently available on the market for producing an over-edge butt-seam at the edges of the carpet rolls has proven itself to be unreliable in that the moving parts tend to wear out or come out of adjustment frequently, leading to costly equipment down time. Further, the machine cannot sew both backed and unbacked goods satisfactorily.
A strong need continues to exist for a machine which will provide a reliable over-edge stitch in both backed and unbacked carpet which will allow the sewn edges to be flattened out into a substantially planar configuration for further processing of the joined carpet rolls in the mill.
It is therefore a principal object of the present invention to provide a machine which is capable of sewing an over-edge stitch at the edges of thick materials, such as tufted carpet, which will allow the materials at the seam to be flattened out after stitch is formed.
It is a further object of the present invention to provide a machine design for sewing an over-edge butt-seam at adjoining edges of two carpet rolls, wherein only a relatively small number of parts of an existing machine are replaced by parts specially designed to sew a wider, looser seam at the edges of the two carpet rolls.
It is a further object of the present invention to provide a workpiece or carpet guide having an extension arm adapted to retain several of the over-edge loops of previously formed stitches thereon, thereby substantially prohibiting a tightening of the previously formed stitches as the sewing operation progresses.
It is a further object of the present invention to provide a looper and guide assembly for producing a wider and looser stitch which is compatible with an existing over-edge sewing machine.